The Sharpless catalog of emission nebulae contains 313 entries representing H-II emission nebulae with a declination of -27 degrees or above. Compiled and published by American astronomer Stewart Sharpless (USNO) in 1959 (see here), the catalog contains a wide variety of star formation regions across the Milky Way including various Herbig-Haro and Wolf-Rayet objects as well as a number of well-known emission nebulae such as the Trifid (M20), the Eagle (M16), Orion (M42), Lagoon (M8), the Crescent (NGC 6888), and the Crab (M1) nebula.

Note: The large and bright emission nebula Sh2-157 in Cassiopeia (near the northern border with Cepheus) lies 8,150 light-years away and spans another 215 light-years across. Sh2-157 is described as a ring nebula surrounding the Wolf-Rayet star WR 157 (SAO 20512, mag 9.58) and is in the immediate vicinity of both the open cluster M52 as well as the stunning Bubble Emission Nebula. Also visible in the field of view of the image below is the small open cluster NGC 7510 at the top right quadrant which is comprised of approximately 100 member stars, is well-detached from the background and is relatively bright at mag 7.9. Similarly, the bottom right quadrant has the small elliptical planetary nebula PLN 110-0.1 (aka WeSb 6, RA: 23h 12m 12s, Dec: +59°36'02") with an apparent diameter of two arc-minutes.